It is increasingly common in the automotive industry to attach boot lids to car bodies using a pair of four-link hinges, each hinge comprising a body link and a lid link and the body and lid links being joined by long and short links. When the boot lid is closed the hinges collapse into the shallow gutters on each side of the boot between the boot lid and the external surface of the car body.
Such four-link hinges have the advantage, over conventional swan-neck hinges, that they do not intrude into the boot space when the boot lid is closed.
Assistance in opening the boot lid is usually provided by a gas strut acting on each hinge, and since it is undesirable for the struts to intrude into the boot space, it is necessary for them also to be located in the shallow gutters. However, the almost horizontal attitude of the struts when the lid is closed results in the struts providing a poor mechanical advantage, and therefore little assistance during the initial opening of the lid.
Various mechanisms have been proposed to assist the initial opening of such hinges, but to the best knowledge of the applicant, no mechanism to date has been operable to open the hinge to a greater extent than approximately 20° of rotation of the lid link relative to a closed position. It is believed that the minimum extent to which the hinge must be opened for the gas strut to be operable to open the hinge fully is approximately 35° of rotation of the lid link relative to the closed position.